It’s also just one of just six screenfold books that were penned before Cortez started his conquest of Mexico’s indigenous people.

So suffice to say that it’s a pretty exceptional record of the pre-Spanish Mesoamerican world.

This codex is called a screenfold book because Aztec scholars would literally twist and fold the 22-page, double-sided document to cross-reference a particular date to two calendar cycles: the yearly cycle of 365 days and the sacred cycle of 260 days (called tonalpohualli).

“In the hands of ritual practitioners and other high-ranking individuals, the codex became a guide for people’s actions. The screenfold’s internal reading structure is right to left and is determined by the number-and-sign sets of the calendar: how the images and symbols cross-referenced each other was then interpreted by the reader, who was well versed in the significance of the various icons. Although an object of great respect, the codex was also a tactile, malleable reference tool: a user could consult both sides simultaneously by folding parts of the codex onto itself. Reading it offered guidance on appropriate days to travel, to celebrate a deity’s beneficence with sacrifices, to plant crops or to name a child.”

These days the codex is not twisted and folded as it once was. In fact, it doesn’t get handled much at all due to the animal-skin document’s fragility and worth. When Mesoamerican experts want to study the codex, they typically have to rely on photographs, Ostapkowicz notes.

The last page of the Aztec Codex Fejérváry-Mayer. Credit: Liverpool's World Museum.

A very rare exception was made a few weeks ago when MOLAB, a nomadicteam of conservation scientists from Italy, drove up to Liverpool to help museum staff study the pigments, dyes and binders used to make the codex.

The MOLAB team has a battery of snazzy equipment that can study fragile artwork without taking a sample of it—in the same way that an X-ray, ultrasound or MRI can give doctors insight about what’s going on inside a patient without invasive surgery or removal of a blood sample.

In the case of the codex, the analytical equipment used by the scientists relies on X-rays and infrared light to diagnose the document’s inner make-up.

I’m really looking forward to what the researchers find, once all the data is analyzed. As Ostapkowicz puts it, the experiments were “an unprecedented opportunity” to safely study the codex.

It’s work that will inform what conservators do to keep the fragile artifact in good shape for many tonalpohualli cycles to come.

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